[FFmpeg-user] Increase video speed via framerate change?

[Henk D. Schoneveld]

On 30 Oct 2013, at 13:20, Richard llom <richard.llom at gmail.com> wrote:

> Hello,
> I have an video with 4 fps, I want to speed this up (time lapse), but also 
> increase the framerate, so I thought:
> ffmpeg -i input.ogv -r 12 output.webm
You’ll have to apply a little more thought to this. You have to encode, so tell ffmpeg which encoder library to use. ffmpeg -i file -c:v libx264 
chooses libx264 as encoder library. Further you have to tell ffmpeg what the input frame rate is AND what output framerate you want it to become. Search the web for examples.
Henk
> 
> will do the trick, but no avail. Video is still the same length, how can I 
> do this in ffmpeg?
> 
> TIA
> richard
> 
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